1. Field of the Invention
The present invention relates to porous matrices which are based on a biologically tolerated polymer or polymer mixture, to cell implants which build on the latter, to other cell implants which are based on cell mixtures composed of hepatozytes and islet of Langerhans cells, to a method for preparing porous matrices and to the matrices which can be obtained using this method, and to a special method for obtaining cells for inoculating an implantable matrix.
2. Description of Related Art
Tissue engineering is an interdisciplinary field which combines engineering and material sciences with medicine. The aim is to restore damaged tissue or improve its function.
The principle of tissue engineering is extremely simple: some cells are first of all removed from the patient and propagated in vitro. The propagated cells can then be embedded in a framework substance, resulting in the formation of a complete, live tissue replacement which is transplanted once again into the patient. In contrast to a conventional allogenic transplantation, which presupposes a suitable donor and as a rule requires life-long medicinal immuno-suppression, this method offers the crucial advantage of being able to use endogenous (autologous) cells.
The nature and construction of the framework substance employed, which is also termed matrix in that which follows, is of particular importance for the implants being accepted and being able to function. Apart from the material to be used, which is namely as a rule biologically degradable polymers, pore size, porosity and surface, just like pore shape, the morphology of the pore wall, and the connectivity between the pores, play a crucial role for the further development of the cells which are embedded in the framework substance and ultimately for the three dimensional construction of the tissue or organ to be regenerated.
Methods for producing biomatrices of this nature have already been disclosed. Thus, techniques from the textile field have already been applied for producing woven and nonwoven fibrous biomatrices. Another common method, in which salt crystals are first of all worked in to the biologically degradable polymer and then dissolved out again, makes it possible to control the pore size by way of the size of the salt particles and to control the porosity by way of the salt/polymer ratio (WO 98/44027). In a modification of the method, the biologically degradable polymers, which are dissolved in a solvent, are applied to what is termed a porogenic material, which is then once again dissolved out of the composite material, resulting in pores having the shape of the negative image of said porogenic material being left behind (WO 01/87575 A2). Coated matrices have also already been disclosed (see, for example, WO 99/09149 A1).
Nevertheless, the biomatrices which have thus far been produced using this method are not satisfactory in every case, in particular with regard to the acceptance and functional capacity of the implants which build on these matrices. In particular, no acceptable organ replacements have thus far been achieved using liver and pancreas implants.